Effect of wind on foliage obstructed line-of-sight channel at 2.5 GHz

A fixed terrestrial broadband wireless system such as MMDS (Multipoint Microwave Distribution System) is a cost effective solution for cable coverage to the immediate surrounding rural area. This wireless system can be operated with the existing cable headend and the same subscriber-end cable modem. Such a system works well with clear line-of-sight transmit/receive antennas. However, in near-line-of-sight transmission where a few foliated trees block the line-of-sight, signal distortion can occur, especially under conditions of high wind. The motion of the trees causes large and rapid signal fading. Measurements were taken on fixed wireless paths blocked with a few trees in the vicinity of the receive antenna. Fading characteristics of a 6 MHz channel centered at 2.545 GHz are provided. The fades are largely flat across the band but with some frequency selective fading. Fading rates under windy conditions ranged from 0.5 to 2 fades/second. The slope of the fades occasionally reached 50 dB/second.